Global environmental issues are being recognized on a global-scale. As one countermeasure, the use of natural energy such as photovoltaics is drawing attention. In general, photovoltaics is easily affected by the weather, making the output of generated electricity unstable. As a result, various techniques are present to achieve effective utilization.
According to one method of coping with the instability of photovoltaics, storage cells and other types of distributed power sources such as fuel cells are operated according to an operation plan. This operation plan, for example, is a control parameter for suitably controlling the discharge of electricity from a storage cell, which has a limited capacity. For example, when power demand exceeds a given power value and a peak cut scheme of discharging the storage cell is used as a storage cell control scheme, this power value is the operation plan. In the operation of a combination of photovoltaics and storage cells, typically, storage cell operation is simulated based on predicted shifts in power demand and predicted weather changes for the following day, and the operation plan for operating the storage cell for the day is created such that an assessment value is optimized, the assessment value being a simulation result in a case where the power demand shifts as expected.
For example, according to one operation method, the operation plan is corrected during storage cell operation. Typically, a prediction made after checking weather conditions on a given day has a higher degree of certainty than a weather prediction made the day before. Thus, when the weather forecast made the day before is off, by correcting the implemented operation plan based on weather conditions confirmed on the day, the operation state of the storage cell is improved.
For example, according to another method, a storage cell operation plan is created by performing simulation based on correction of the operation plan when a forecast deviates from actual weather conditions. In this method, based on data concerning past power supply and demand, predicted deviation patterns in which a predicted value of the power supply and demand is off by a constant value or more and the occurrence probabilities thereof are preliminarily collected. An assessment value is obtained by performing a simulation for each predicted deviation pattern. The assessment value takes correction of the operation plan when the forecast deviates from actual weather conditions into consideration. Subsequently, an operation plan that considers cases where the forecast deviates from the actual weather conditions is created based on an overall assessment value obtained by weighting the assessment values when the forecast is correct, with the assessment values obtained for the predicted deviation patterns, according to the respective occurrence probabilities and adding the results. For examples of such technologies, refer to Japanese Patent No. 4245583; and Japanese Laid-Open Patent Publication Nos. 2005-86953 and 2008-141918. Further examples are discussed by Mitsuro KUDO, et al in “Forecasting Electric Power Generation of Photovoltaic Power System”, The Institute of Electrical Engineers of Japan Academic Journal B, Vol. 127 (2007), No. 7, pp. 847-853; and by Satoshi TAKAYAMA, et al in “A Study on the Scheduling of Large-Scaled PV Power Station Output based on Solar Radiation Forecast”, The Institute of Electrical Engineers of Japan Academic Journal B, Vol. 129 (2009), No. 12, pp. 1514-1521.